Avoid ambiguous implicit errors with dotty

For a Boolean b and a prop p, the following is ambiguous in dotty:
b ==> p
Because we have:
  implicit def BooleanOperators(b: => Boolean) = new ExtendedBoolean(b)
  implicit def propBoolean(b: Boolean): Prop = Prop(b)

And both ExtendedBoolean and Prop provide a `==>` method, the one in
`ExtendedBoolean` just forwards to the one in `Prop`. This is not
ambiguous in scalac because `Boolean` wins against `=> Boolean` but it
is in dotty.

This commit fixes this by removing the `==>` method from
`ExtendedBoolean`, this may break code that explicitly imported
`BooleanOperators` but not `propBoolean`, the fix is to also import `propBoolean`.

jvm/src/test/scala/org/scalacheck/PropertyFilterSpecification.scala

@@ -9,7 +9,7 @@
 
 package org.scalacheck
 
-import Prop.BooleanOperators
+import Prop.propBoolean
 
 object PropertyFilterSampleSpecification extends Properties("PropertyFilterSample") {
 

jvm/src/test/scala/org/scalacheck/ShrinkSpecificationJVM.scala

@@ -1,6 +1,6 @@
 package org.scalacheck
 
-import Prop.{forAll, BooleanOperators}
+import Prop.{forAll, propBoolean}
 import Shrink.shrink
 import ShrinkSpecification.shrinkClosure
 

jvm/src/test/scala/org/scalacheck/examples/StringUtils.scala

@@ -52,7 +52,7 @@ object StringUtils extends Properties("Examples.StringUtils") {
   }
 
   property("truncate.precond") = Prop.forAll { (s: String, n: Int) =>
-    import Prop.BooleanOperators
+    import Prop.propBoolean
     (n >= 0) ==> {
       val t = StringUtils.truncate(s, n)
       (s.length <= n && t == s) ||

src/main/scala/org/scalacheck/Prop.scala

@@ -330,31 +330,11 @@ object Prop {
     def =?(y: T) = Prop.=?(x, y)
   }
 
-  /** A collection of property operators on `Boolean` values.
-   *  Import [[Prop.BooleanOperators]] to make the operators available. */
-  class ExtendedBoolean(b: => Boolean) {
-    /** See the documentation for [[org.scalacheck.Prop]] */
-    def ==>(p: => Prop) = Prop(b) ==> p
-    /** See the documentation for [[org.scalacheck.Prop]] */
-    def :|(l: String) = Prop(b) :| l
-    /** See the documentation for [[org.scalacheck.Prop]] */
-    def |:(l: String) = l |: Prop(b)
-    /** See the documentation for [[org.scalacheck.Prop]] */
-    def :|(l: Symbol) = Prop(b) :| l
-    /** See the documentation for [[org.scalacheck.Prop]] */
-    def |:(l: Symbol) = l |: Prop(b)
-  }
-
   /** Implicit method that makes a number of property operators on values of
    * type `Any` available in the current scope.
    * See [[Prop.ExtendedAny]] for documentation on the operators. */
   implicit def AnyOperators[T](x: => T)(implicit ev: T => Pretty): ExtendedAny[T] = new ExtendedAny[T](x)
 
-  /** Implicit method that makes a number of property operators on boolean
-   * values available in the current scope. See [[Prop.ExtendedBoolean]] for
-   * documentation on the operators. */
-  implicit def BooleanOperators(b: => Boolean): ExtendedBoolean = new ExtendedBoolean(b)
-
   /** Implicit conversion of Boolean values to Prop values. */
   implicit def propBoolean(b: Boolean): Prop = Prop(b)
 

src/main/scala/org/scalacheck/commands/Commands.scala

@@ -127,7 +127,7 @@ trait Commands {
     /** Wraps the run and postCondition methods in order not to leak the
      *  dependant Result type. */
     private[Commands] def runPC(sut: Sut): (Try[String], State => Prop) = {
-      import Prop.BooleanOperators
+      import Prop.propBoolean
       val r = Try(run(sut))
       (r.map(_.toString), s => preCondition(s) ==> postCondition(s,r))
     }

src/test/scala/org/scalacheck/PropSpecification.scala

@@ -12,7 +12,7 @@ package org.scalacheck
 import Prop.{
   forAll, falsified, undecided, exception, passed, proved, all,
   atLeastOne, sizedProp, someFailing, noneFailing, Undecided, False, True,
-  Exception, Proof, throws, BooleanOperators, secure, delay, lzy
+  Exception, Proof, throws, propBoolean, secure, delay, lzy
 }
 import Gen.{ const, fail, oneOf, listOf, Parameters }
 

src/test/scala/org/scalacheck/ShrinkSpecification.scala

@@ -9,7 +9,7 @@
 
 package org.scalacheck
 
-import Prop.{forAll, forAllNoShrink, BooleanOperators}
+import Prop.{forAll, forAllNoShrink, propBoolean}
 import Shrink.shrink
 
 import scala.concurrent.duration.{Duration, FiniteDuration}

src/test/scala/org/scalacheck/examples/MathSpec.scala

@@ -1,6 +1,6 @@
 package org.scalacheck.examples
 
-import org.scalacheck.Prop.{forAll, BooleanOperators}
+import org.scalacheck.Prop.{forAll, propBoolean}
 
 object MathSpec extends org.scalacheck.Properties("Math") {
   property("sqrt") = forAll { n: Int =>